A systems approach evaluating alternative dairy feeding strategies in south-east Australia

© 2012 Dr. Şeyda ÖzkanThe Australian dairy industry relies primarily on pasture for its feed supply. However, the variability in rainfall negatively effects plant growth, leading to uncertainty in dryland feed supply, especially during periods of high milk price. New (complementary) systems combining perennial ryegrass with another crop and/or pasture species have potential to mitigate this seasonal risk and improve productivity and profitability by providing off-season feed. To date, the majority of research studying the integration of alternative crops into pasture-based systems has focused on substitution and utilisation of alternative feed sources. There has been little emphasis on the impacts of integration of forage crops on the production of surpluses or deficits in feed supply (pasture and pasture products such as hay and silage) for subsequent lactations. This study, unlike others where pasture consumption is estimated, uses actual annual pasture consumption rates measured over four years from an on-farm trial. In addition, while the ultimate aim of adopting different feeding systems is to increase productivity and profitability of dairy farmers in Victoria, the benefits and costs associated with transitions of systems have to be addressed. These include whether alternative feeding systems produce different amounts of greenhouse gas (GHG) emissions, and whether the proportions of carbon-based and nitrogen-based emissions produced in each system are comparable. Further, if a direct cost is placed on carbon emissions, whether Australian dairy farmers will seek mitigation strategies to reduce their GHG emissions. The impact of a direct price of carbon emissions on dairy farm operating profits has not been widely studied in Australia. This thesis examines and analyses actual systems data from two pasture-based feeding systems trials conducted in southern Australia. The systems examined are a ryegrass-based (RM) system comprising pasture and pasture silage and a complementary forage-based (CF) system comprising double-cropping (winter cereal crop followed by a summer grazing crop) as well as pasture and pasture silage. A comparison of pasture production and pasture consumption profiles of the two pasture systems revealed that both are under supplied during the months of July, December, January, February and March (with at least a 50% probability). Feeding strategies were developed for the rest of the production year when the pasture production exceeded the pasture consumption. The integration of double-cropping systems into pasture-based dairy production systems in south-east Australia was investigated for providing feed at critical times of the production period to further increase milk production. The partial life cycle assessment (LCA) used to evaluate the GHG emissions produced in each feeding system indicated that the RM and the CF systems produced 9.6 t and 12.3 t of carbon dioxide equivalent (CO2-eq) emissions per ha respectively. This equalled to 7.4 kg and 7.1 kg CO2-eq emissions per kg milk solids (MS) produced respectively. A nitrogen (N) surplus balance technique showed that the ratio of N in milk to N in all the inputs used was similar, 25.2% and 26.6%, for the RM and the CF systems respectively. A novel risk analysis comparing the variability in income in response to different prices on carbon emissions was also conducted in this study. Imposing a carbon price ($20–$60) and not changing the systems reduced the operating farm operating profits by 28.4% in the RM systems and 25.6% in the CF system compared to a scenario where no carbon price was imposed. In conclusion, production and utilisation of home-grown feeds will remain paramount among the south-east Australian dairy farmers to maintain and increase profitability in this competitive dairy sector. However, the risk associated with the higher operating profits in the CF system requires further evaluation. There is opportunity for future studies to focus on the impacts of different mitigation and adaptation strategies and policy impact on farm operating profit. Further evaluation and improvement of the assumptions and model predictions as well as the monitoring technologies are suggested to enable further policy research